1. FIELD OF THE INVENTION
The present invention is directed to a screen device for use in a subterranean well and securable on a conduit as a "pre-packed" gravel packing screen. The screen may be used alone to filter particulate matter entering in the conduit with the produced hydrocarbons, or in combination with known gravel packing procedures in the well, to further filter such fluids.
2. BRIEF DESCRIPTION OF THE PRIOR ART
When oil and gas wells are drilled through formations which generally are of an unconsolidated nature, the produced fluids can be expected to contain said particulate matter, generally referred to as "sand". It is undesirable to produce such particulate matter with the production fluids because of abrasion of production tubing, valves and other equipment used to produce the well and carry such fluids from the well, through the sales line, and the like. It is therefore necessary in such instances to avoid production of such sand and other particulate matter with the fluids.
In the past, those skilled in the art have reduced the production of sand by "gravel packing" the well during completion operations. Such gravel packing includes providing on the production conduit or tubular work string a device including a slotted or ported cylindrically shaped member which prevents the passage therethrough and into the interior of the conduit of solid particles exceeding a pre-determinable size. Such devices are incorporated into equipment and methods wherein gravel packing is introduced into the annular area between the production conduit or workstring and the casing of the well, or, in the event of non-cased wells, the well bore wall, with the gravel being deposited longitudinally exteriorly of the slotted or ported cylindrical member.
Gravel packing of such wells has also been effected by means of incorporation onto the production or workstring of a "pre-pack" apparatus, wherein gravel, glass beads, bauxite, or other solid particulate is disposed in between an outer member, such as stainless steel wire wrap screen, and an inner ported member, such that the device may be carried into the well and positioned adjacent the production zone to thereby prevent the particulate matter sand produced with the production fluids from entering the interior of the conduit and being produced to the top of the well with the production fluids. Such "pre-packs" may be used alone or in conjunction with apparatus and method wherein the well bore is also gravel packed.
In order to provide the most effective gravel pack possible within a subterranean well, it is desirable that the gravel pack completely fill and extend from the internal diameter of the casing to the external diameter of the production or workstring, the objective being to provide as large a radial area of gravel pack within the well as is possible. However, this objective has been abated when conventional prior art gravel pack pre-packs run into the well on the production or workstring, because the screen members and housing extend outwardly and away from the outer diameter of the production string, thus restricting the gravel pack directly across the pre-pack tool which has been utilized.
The present invention provides a "pre-packed" apparatus and method for gravel packing a subterranean oil or gas well wherein a retention means having selectively sized openings is provided in the apparatus to prevent a fluid permeable bed of particulate solids among the exterior of the retention means in which is sized to prevent effectively all such particular solids from passing inwardly through the retention means and through the interior of the device and thence through the conduit to the top of the well. The invention further provides and apparatus which provides a slimmer or thinner pre-pack apparatus which conforms more to the outer diameter of the production tubing and collars thereon such that the effective radius of the external gravel pack area is not as reduced as would be when prior art pre-pack screens are utilized, and provides the retention means with a cross-sectional area which is smaller than the cross-sectional area of the outer fluid permeable housing. Additionally, the present invention provides a "pre-packed" apparatus and method which has the retention means directly interfacing circumferentially around and on the inner tubular member.
The prior art contains a number of references to gravel packing methods and apparatuses incorporating slotted, ported or wire-wrapped screen devices which have disposed therein particulate matter, such as glass beads, gravel and the like, including the following U.S. patents:
______________________________________ Patent No. Title ______________________________________ 1,218,848 STRAINER FOR PUMPS 2,190,989 METHOD OF PREPARING AN OIL WELL FOR PRODUCTION 2,371,385 GRAVEL PACKED LINER AND PERFORA- TION ASSEMBLY 2,523,091 OIL-WATER SEPARATOR FOR WELLS 2,525,897 WELL PIPE FILTER 2,530,223 OIL WELL FILTER 2,877,852 WELL FILTERS 2,978,033 DRILLABLE PREPACKED SAND CONTROL LINER 2,981,332 WELL SCREENING METHOD AND DEVICE THEREFOR 3,261,401 WATER PRODUCTION 3,455,387 WELL COMPLETION TECHNIQUE AND APPARATUS FOR USE THEREWITH 4,494,603 WIRE MESH WELL SCREEN WITH WELDED WIRE SUPPORT 4,583,594 DOUBLE WALLED SCREEN-FILTER WITH PERFORATED JOINTS 4,526,230 DOUBLE WALLED SCREEN-FILTER WITH PERFORATED JOINTS 4,649,996 DOUBLE WALLED SCREEN-FILTER WITH PERFORATED JOINTS ______________________________________
In the present invention, it has been found that a retention means may be utilized to prevent the entry into the interior of the device of sized members of a particulate filtering bed, such as sand, bauxite, resin coated sand, and the like. Such device permits the sized particulate matter bed to be the primary filtering medium to effectively filter particulate matters out of the produced hydrocarbons in the subterranean well, thus permitting such produced hydrocarbons to pass freely of said particulate matter into and through said apparatus and said conduit to the top of the well. A secondary filtering means is defined by the retention means which, in turn, prevents effectively all of the particles in the fluid permeable bed from passing through the retention means to the interior of the apparatus and through the conduit to the top of the subterranean well with the produced hydrocarbon fluids.
In co-pending U.S. Pat. application Ser. No. 206,209, filed June 13, 1988, entitled "GRAVEL PACKER APPARATUS", and assigned to the same assignee as the present application, the disclosure of which is hereby incorporated by reference, there is disclosed as a portion of said application a gravel packing screen device incorporating a wire mesh screen. In such application, the wire mesh screen serves as the primary filtering medium through which the produced hydrocarbons in the well may pass freely through the wire mesh screen and into the interior of the apparatus through the conduit to the top of the well substantially free of solids produced in said well. The present invention differs from said invention in that the retention means of the present invention does not act as the primary filtering medium for the well fluids, but, in effect, retains the particulate matter of the primary filtering medium, which is the fluid permeable bed of particulate solids, within the apparatus and prevents them for entering into the interior of the apparatus with the produced hydrocarbons.